In the clothing store there is a sister named Sable always on a sewing machine. Once every day you need to talk to her and slowly, she'll become friends with you. When that happens, she'll let you use her other sewing machine which is the QR machine.

"In the Able Sisters' shop, you can unlock a QR code machine that creates a QR code that represents a custom design. Other players can then scan this code to get your custom designs into their games. To unlock this, talk to Sable, who is working at the sewing machine. You have to talk to her each day for several days in a row. Then the QR code machine will be unlocked."

Animal Crossing New Leaf: Able Sisters

"The clothing (left) side of the store is the larger part. The clothing side is run by Sable and Mable, and they sell shirts, pants, dresses, and skirts.You can also make your own patterns, and share the via QR code.The QR code machine will become unlocked after you befriend Sable (speaking to her for ~10 days) - once you have befriended her the QR machine will appear and allow you to scan QR codes; If you want to know more about QR codes and patterns, watch this video.If you are interested in finding QR codes for yourself, check out this page, which has a collation of QR codes I’ve come across."

_____________________________________________

Hope this helped!

Signature--------------
While the whole World is laughing at you,
God is smiling down, thinking, "They have no idea what she is capable of."

I had unlocked it yesterday, but when I went to use it today, I talked to her and she just gave me a "..." like it was Day 1 again!! Anyone else have this happen? It bummed me out, I really don't want to go through another 14 days of that...